Sound is too thin. What to upgrade, add or remove?

Need your advise - please have a look at my system below (click on the system link). Just in the past couple of months or so it seems, my setup started to sound way too thin in my ears. It feels as though the bottom-end is just not enough anymore. But I as you can see from the pictures, I try to stay on the minimulist side of things. The aesthetics are very important as well (WAF). I can't really have too much exposed gear (WAF). What can I do to boost the overall sonics of this system without adding a sub? How much more can a power conditioner add? What about replacing the power tubes, IC's and adding a DAC? or should I switch to a different amp - like a Gamut (SS) 200/wcp? What other push-pull (100 wpc or more) quality tube amps are out there? My budget is $2K - $3K plus the value of current amp if I were to swap it out.

I really appreciate your comments. Thank you.

Jewel